Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

444
FXUS63 KLOT 070526
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1226 AM CDT Tue Apr 7 2026

.KEY MESSAGES...

- Sub-freezing temperatures expected tonight, but warmer
  conditions develop Wednesday and into the weekend.

- Brief chance for a light wintry mix Tuesday night, mainly
  near the IL-WI stateline.

- Periods of showers and storms are possible late in the week
  into next weekend.

&&

.DISCUSSION...
Issued at 129 PM CDT Mon Apr 6 2026

A broad surface high continues to reside over the northern
Plains and will be drifting southward into northern IL and
northwest IN on Tuesday. Ahead of the high is a frontal boundary
that is stretching from northeast IA to the eastern UP of MI.
As the high begins to drift towards the area tonight, this
frontal boundary will get forced southward and become enhanced
by the cooler air of Lake Michigan. While the frontal boundary
will not result in much impactful weather for most, there
remains a signal for some isolated to widely scattered showers
to develop near the lake this evening into early Tuesday
morning. The reason is due to some modest lake induced
instability that is forecast to materialize just ahead of the
front. However, with the subsidence from the high expected to be
increasing overnight there will likely be some competing
factors and thus confidence on these showers remains low.
Regardless, have opted to maintain a slight (15-20%) chance in
the forecast for snow showers given that temperatures will be
cooling into the mid to upper 20s overnight.

Heading into Tuesday, the surface high will be moving overhead
resulting in mostly clear skies and dry conditions. Though with
winds expected to be out of the east-northeast, cooler
temperatures are forecast with highs in the mid-40s inland with
readings only in the mid to upper 30s near the lake.
Unfortunately the surface high will not hang out long as a weak
shortwave will be ejecting out of the central Plains Tuesday
night which will in turn push the high east of the area.
Associated with this subtle shortwave will also be an area of
precipitation that will be lifting northward on a mid-level
frontal boundary Tuesday night. Given that moisture across
northern IL and northwest IN looks to be somewhat limited, it
appears that the coverage from any precipitation will be more
scattered and mainly focused north of I-80. That said, as
precipitation begins temperatures should be cold enough (in the
upper 20s to lower 30s) for the precipitation to start off as
snow but as the frontal zone lifts through, temperatures (both
at the surface and aloft) should be slowly warming overnight and
could result in a brief period of a wintry mix especially near
the IL-WI line. With forecast soundings during the precipitation
not showing a ton of mid-level warming it appears that the
favored precipitation type would be snow with perhaps some sleet
mixed in before things go over to rain but there is a 10-15%
chance that some freezing rain could occur if mid-level
temperatures warm enough. Regardless, the short duration and
moderating temperatures should keep any snow or ice accumulation
at a minimum so no impacts are expected.

Any precipitation Tuesday night should taper by daybreak
Wednesday resulting in another dry day. Temperatures on
Wednesday will also continue to warm with highs in the mid to
upper 60s. Though winds on Wednesday will also be gusty out of
the southwest with speeds peaking around 30-35 mph during the
afternoon. In fact, if deeper mixing is achieved some locally
higher gusts could even be seen.

While we enjoy another mild spring day on Wednesday, an upper
low is forecast to be moving across the northern Plains towards
the Great Lakes with its associated surface low. Attached to the
low will be a cold front that will be stretching from WI to KS
that will move into northern IL and eventually northwest IN
Wednesday night. Initially some scattered showers (and perhaps
even a couple of thunderstorms) should be ongoing along the
front, but as the front moves into our area the drier air in
place looks to cause the showers to become more isolated. Thus
rain chances will actually be diminishing as the front
progresses through the area. Since the front is forecast to
stall overhead on Thursday it seems that the areas that miss out
on rain Wednesday night will have a shot for it on Thursday.
Furthermore, with the stout southwesterly flow pattern aloft.
Given that convection often manipulates boundary positions and
how poorly the courser global guidance handles this shift,
confidence the exact timing and placement of the showers and
storms this weekend is somewhat low. Nevertheless, ensemble
guidance does suggest that some instability will materialize on
Thursday and result in some scattered showers and thunderstorms
especially across the southern half of the area. Though with the
weaker shear profiles (around 30 kts) it appears that the
threat for severe weather is low at this time.

This frontal boundary is not expected to move much Thursday
night into Friday which looks to result in continuous rounds of
showers and embedded thunderstorms. In fact, with storm motions
currently forecast to be parallel to the frontal boundary
conditions do look favorable for training convection which could
result in localized threat for flash flooding, especially if
storms overlap areas that saw heavy rainfall this past weekend.
Outside of the rain, temperatures for Thursday and Friday look
to remain seasonably warm with highs in the 60s to around 70
each day (warmest south of the aforementioned boundary).

As for the upcoming weekend, this frontal boundary is forecast
to hang around the southern Great Lakes and Ohio River Valley
regions through the weekend and will serve as the focus for
additional period of showers and thunderstorms as several
shortwaves are projected to traverse the southwest flow pattern
aloft. Given that convection often manipulates boundary
positions and how poorly the coarser global guidance handles
this shift, confidence the exact timing and placement of the
showers and storms this weekend is somewhat low. Nevertheless,
ensemble guidance does suggest that most areas could see upwards
of 1-2 inches of rainfall by the end of the weekend (30-40%
chance). With the already swollen streams/rivers, this
additional rainfall will likely keep the river flood threat
around and could even result in some localized urban flooding as
well.

Yack

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 1226 AM CDT Tue Apr 7 2026

Key Aviation Messages for the current TAF period:

- Lingering MVFR cigs and breezy northeast winds through 09Z
  around Chicago terminals

- Northeast winds becoming easterly, then eventually southeast
  after 06Z

- Less than a 30 percent chance for precipitation overnight
  into Wednesday morning

Winds have turned to the northeast across the forecast area.
Breezier winds remain closer to Lake Michigan where a localized
MVFR cloud deck remains parked over the city. Low confidence on
exact timing, but winds are expected to gradually diminish and
the lower clouds should scatter out in the next few hours.

VFR conditions are expected through Tuesday as winds turn to
the east. As a surface ridge gradually drifts eastward, winds
will gradually turn to the southeast (in the afternoon closer to
KRFD and after 06Z for Chicago terminals). A weak embedded wave
is expected to pass over northern Illinois which may include
the chances for precipitation tonight. However, confidence is
low on the details due to models disagreement on the strength of
the forcing, the exact track of the wave, and low level
temperatures. Since the chances for precipitation after 06Z
remain less than 30 percent, it was decided to keep the TAFs dry
at the moment (although the better chances may be closer to
KRFD, which is outside its` current TAF window). In terms of
precipitation type with this wave, temperatures are going to
start out cold enough for snow tomorrow night. Warm air
advection into the region will help turn snow over to rain and
potentially even have a short window of some wintry mix (sleet
and/or freezing rain). Any snow accumulations (IF they occur)
would be nothing more than a dusting.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 1 PM CDT this afternoon for the IL
     nearshore waters.

     Small Craft Advisory until 4 PM CDT this afternoon for the IN
     nearshore waters.

&&

$$

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